As well known, a glass bulb employed in a CRT for use in a color television or a computer monitor includes a panel for displaying an image, a conical funnel portion joined to a rear portion of the panel and a cylindrical neck integrally connected to an apex portion of the conical funnel portion. The panel, the funnel and the neck portion are made of glass, and particularly the panel and the funnel portion are formed with predetermined dimensions and shapes by press-forming a melted glass called a glass gob.
Such a CRT panel is provided with a faceplate for displaying an image, a skirt portion extending backward from a perimeter of the faceplate and having a seal edge on its back end, and a blend round portion (or corner portion) integrally joining the skirt portion to the faceplate. The funnel is divided into a body portion having a seal edge and a yolk portion extending backward from the body portion. The seal edge of the body portion is connected to the seal edge of the skirt portion, and the neck portion is connected to the yolk portion.
Recently, a flat panel tends to be preferred to a conventional spherical panel because of customers' increasing demand for high resolution and large-size screen, thereby rapidly accelerating the replacement of the spherical panel by the flat panel. When compared to a spherical panel, a flat panel offers numerous advantages. For example, the flat panel can reduce image distortion, minimize eye fatigue and provide a wide range of visibility. However, a CRT with a large-size screen increases the total depth of the CRT, i.e., a distance between the faceplate and the rear of the neck portion, thereby occupying large space. Hence, the CRT having a large-size screen is disadvantageous over a flat display such as a plasma display-panel (PDP) and a liquid crystal display (LCD) with a same-size screen in terms of saving space needed for installation thereof.
Therefore, various attempts have been made to reduce the total depth of the CRT as well as to enlarge and flatten the screen thereof. In such attempts, however, a shadow mask and an inner shield become an obstacle to the reduction of the total depth. In a beam index CRT, which eliminates the shadow mask and the inner shield and employs an index stripe and a photo detector, a complete flattening and a slimness of the panel can be achieved. A sheet glass substrate without the skirt portion is used as a flat panel for a small CRT of a size ranging 15˜19 inches. However, in case the sheet glass substrate is used as a flat panel for a large CRT of a size of 29 inches or greater, it is difficult to manufacture the sheet glass substrate due to its deformation occurring upon the press-forming thereof and further, the sheet glass substrate is structurally so weak that it does not satisfy UL (Underwriters Laboratories Inc.) standards for implosion proof.